The present invention relates to a towable dolly for towing a four wheeled vehicle with another vehicle such as a passenger car or a pickup truck not normally equipped for towing. More particularly, it relates to a towing dolly with a "wheel lift" towing system.
Disabled vehicle towing has long been recognized as a problem for persons who do not have access to the traditional tow truck or to those to whom the purchase of such a single-purpose vehicle is not economically attractive. Diverse types of towing dollies for towing a vehicle without a tow truck have been proposed as solutions to this problem.
Typically, such dollies have a frame with road-engaging wheels and a hitch for detachably connecting the frame to the towing vehicle. Many of the dollies have a hoisting device for elevating one end of the vehicle to be towed. In all towing dollies, one end of the vehicle being towed is supported on the road surface by its wheels and the wheels at the other end are supported by the dolly out of engagement with the road surface. The hoisting device of such towing dollies is generally affixed to a bumper, undercarriage, or axle of the towed vehicle. Such attachment devices cannot be used with certain vehicles with collapsible bumpers and/or easily deformed panels without damaging the towed vehicle because such bumpers and/or panels are in contact with the lifting mechanism and cannot structurally withstand the weight of one end of the vehicle being towed.
In addition, modern automobiles may be of unibody construction such that pressure unevenly applied to the vehicle by the lifting mechanism, e.g., during turns, may torque and crack the unibody.
As shown in FIG. 1, existing dollies generally include a wheeled frame removably attached to a towing vehicle such as a car by a conventional ball and cup trailer hitch. Such frames provide an inclined rail 10 on which a carriage 12 may ride under the influence of an electric wrench 14. The carriage 12 generally includes a pair of straps 16 which terminate with hooks of other fittings adapted to engage the bumper, frame, or axle of the towed vehicle. Because the forwardmost point of contact with the towed vehicle is adjacent the extreme front and (rear end if rearward facing as illustrated in FIG. 1), the weight of the towed vehicle is quickly positioned vertically over, or forward of, the axis of the wheels 18 of the dolly even though the wheels of the towed vehicle remain rearward thereof.
Towing dollies of this type are shown, for example, in U.S. Pat. Nos. 3,627,154 to Troup dated Dec. 14, 1971, No. 3,827,586 to Lambert dated Aug. 6, 1974, No. 3,896,949 to Shipley dated Dec. 5, 1973, and Design Patent No. 288,912 to Lucas dated Mar. 24, 1987.
A towing system has been developed which does not attach to the towed vehicle's bumper, undercarriage, or axle. In such system, the towing mechanism lifts the wheels of the towed vehicle, leaving the vehicle riding on its own suspension system. Such systems are referred to herein as "wheel lift" towing systems.
While wheel lift systems avoid damage to the towed vehicle, there has been a significant problem in their use. Such systems, lifting as they must at a point well to the rear of the wheels of the towing vehicle, have been confined in use to tow trucks and other vehicles with weighted front ends, such weight being necessary to resist the tendency of the lifting mechanism, with its large moment arm, to lift the front end of the towing vehicle rather than that of the towed vehicle. U.S. Pat. No. 4,737,066 to Allison dated Apr. 12, 1988, and No. 4,741,661 to Carey dated May 3, 1988 are exemplary of such wheel lift systems.
Thus, while the wheel lift mechanism is highly desirable for towing dollys, the longer reach from the axis of the road-engaging wheels of the towing dolly to the wheels being lifted requires that lifting mechanism extend under the vehicle without contacting the vehicle's frame or bumper a distance which has presented an insurmountable obstacle. When the towed vehicle is being elevated, the longer moment arm tends to rotate the front end of the dolly about the axis of its road-engaging wheels and to produce a highly undesirable negative tongue weight.
It is accordingly an object of the present invention to provide a novel wheel lift towing dolly which obviates many of the problems of known dollies.
It is another object of the present invention to provide a novel towing dolly for lifting one end of a towed vehicle without contacting the frame, bumper, or axle thereof.
It is yet another object of the present invention to provide a novel towing dolly with a pair of horizontally disposed wheel lifting arms carried by a carriage on a single inclined rail without unacceptable torquing of unibody vehicles.
It is still another object of the present invention to provide a novel towing dolly capable of lifting the wheels of a towed vehicle vertically over or forward of the wheels of the towing dolly to provide a positive tongue weight.
It is a further object of the present invention to provide a novel wheel lift towing dolly with means for preventing rotation of the dolly about the axis of its wheels during elevation of one end of the towed vehicle.
It is yet a further object of the present invention to provide a novel wheel lift towing dolly which does not require movement by the towed vehicle to load.
It is still a further object of the present invention to provide a novel wheel lift towing dolly in which the angle of lift may be selectively varied.
It is yet still a further object of the present invention to provide a novel wheel lift towing dolly with a simplified wheel supporting arm mechanism.
It is yet still another object of the present invention to provide a novel wheel lift towing dolly in which the wheel supporting arms move laterally outward into wheel engaging position.
It is another object of the present invention to provide a novel dolly capable of lifting a vehicle from either end. It is yet still another object of the present invention to provide a novel wheel lift mechanism assisted by an inflatable bag.
It is yet still a further object of the present invention to provide a novel dolly with an inflatable lift.
These and many other objects and advantages will be readily apparent to one skilled in the art to which the invention pertains from a perusal of the claims, the appended drawings, and the following detailed description of preferred embodiments.